I'd like to try an experiment here.
A good friend and a fine film maker recently confided that he did not follow all the talk about HD. He was too busy making movies to follow all the tech-talk. That made me realise that my own knowledge was hazy. I started doing some research on the web and found that it is a field with many, many complications.
The Experiment
Can we in this thread try to define as simply as possible what HD is only as it affects PAL systems (to avoid the extra confusion caused by arrangements for NTSC.) We should try to explain what it means when we talk about camcorders, television sets and projectors.
My starting point is that true HD means a picture consisting of 1920 pixels width and 1080 lines height.
There is a partial HD using 1280 pixels width and 720 lines height - better than our current standard definition but not as good as it gets.
Pictures may be displayed as (p) progressive - where the whole picture frame is built up in a fraction of a second
or as (i) interlaced - where like standard definition- each frame is built in two halves: lines (1,3,5 etc) in one pass and lines (2,4,6 etc) in the next.
The number of complete frames presented every second is quoted as "frame rate". For PAL these seem to be only 25 or 50.
Can anyone add any SIMPLE, CLEAR, explanations to this?
Dave
What is HD ?
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Dave Watterson
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Re: What is HD ?
excellent thread Dave.... just wish I could add to it 'technically'!
only to say after much hand wringing and tramping around every shop displaying every possible format of TV I plumped for a Panasonic Full HD (1080p) 100Hz 24p plasma ...
coupled the Z5 up to it...................... absolutely stunning...... no bull.....stunning...
sometimes it pays to jump even when you have nothing else but a gut feeling.... and that what your eyes see 'looks right'...
but any techies out there that want to put it simply would be great !
just a thought...
only to say after much hand wringing and tramping around every shop displaying every possible format of TV I plumped for a Panasonic Full HD (1080p) 100Hz 24p plasma ...
coupled the Z5 up to it...................... absolutely stunning...... no bull.....stunning...
sometimes it pays to jump even when you have nothing else but a gut feeling.... and that what your eyes see 'looks right'...
but any techies out there that want to put it simply would be great !
just a thought...
Stephen
Film making is not a matter of Life and Death
It's much more important than that.
Film making is not a matter of Life and Death
It's much more important than that.
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Dave Watterson
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Re: What is HD ?
OK - already we have added an extra frame rate: 24.
That makes sort of sense ... traditional film has worked for decades at 24 frames-per-second. Most projectors have two or three-bladed shutters so what we usually see on a cinema screen is each frame flashed twice or three times. Again I can see some sense there because anything flashing at less than 70 times a second can seem to flicker - something we learned early on with computer screens. 24 frames a second, each flashed on screen three times would be 72 flashes-per second.
One other important basic point I forgot last night:
HD defines a standard aspect ratio of 16:9.
- Dave
That makes sort of sense ... traditional film has worked for decades at 24 frames-per-second. Most projectors have two or three-bladed shutters so what we usually see on a cinema screen is each frame flashed twice or three times. Again I can see some sense there because anything flashing at less than 70 times a second can seem to flicker - something we learned early on with computer screens. 24 frames a second, each flashed on screen three times would be 72 flashes-per second.
One other important basic point I forgot last night:
HD defines a standard aspect ratio of 16:9.
- Dave
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Roy
Re: What is HD ?
Dave. I think your friend voices the opinion of the vast majority of amateur film makers, they are not bothered to know why something works, the just want to know how to successfully use the product to their advantage.
I'm sure there's a lot of people who, like me. would be baffled by the technical jargon. As Stephen has said,
If somebody can explain things in simple terms, it would be interesting. Alas most people who understand the technical details, lack the means of explaining simply. I also agree that beauty is in the eye of the beholder, and so it is for quality of the video image. e.g. No names no pack drill Stephen, the HD videos you saw at Newcastle recently which you thought were stunning, and maybe they were, but another person who saw the videos, confided that he couldn't tell any difference from the SD videos. All I say is that a £3000 plus a top of the range HD tv should give stunning results. I have to say that I use a cheap sony HDV cam and when I couple that direct to an HD tv, I am more than happy with the image and it does show a marked improvement.
However, having said that, I also find that using a three chip standard Def Panasonic cam coupled with a Grundig HD TV which has a built in upscaler and DVD player, the results are definately not far short of 1018. HD. Also DVD's played back on it show a marked improvement. I am not decrying HD for one minute, I.m all for progress. But I think for most people, it's to early to spend a vast amount of money on a system, which limits you to send Tape of your HD video to the relately few people who have HD cameras tp play back on an HD TV. I know you can use Blu-ray discs, but how many people have blu-ray players and even less have Blu-ray recorders. In conclusion, what counts is the content of the video, and less so the technical details of the equipment used to make it. Don't shoot the messenger.
I'm sure there's a lot of people who, like me. would be baffled by the technical jargon. As Stephen has said,
If somebody can explain things in simple terms, it would be interesting. Alas most people who understand the technical details, lack the means of explaining simply. I also agree that beauty is in the eye of the beholder, and so it is for quality of the video image. e.g. No names no pack drill Stephen, the HD videos you saw at Newcastle recently which you thought were stunning, and maybe they were, but another person who saw the videos, confided that he couldn't tell any difference from the SD videos. All I say is that a £3000 plus a top of the range HD tv should give stunning results. I have to say that I use a cheap sony HDV cam and when I couple that direct to an HD tv, I am more than happy with the image and it does show a marked improvement.
However, having said that, I also find that using a three chip standard Def Panasonic cam coupled with a Grundig HD TV which has a built in upscaler and DVD player, the results are definately not far short of 1018. HD. Also DVD's played back on it show a marked improvement. I am not decrying HD for one minute, I.m all for progress. But I think for most people, it's to early to spend a vast amount of money on a system, which limits you to send Tape of your HD video to the relately few people who have HD cameras tp play back on an HD TV. I know you can use Blu-ray discs, but how many people have blu-ray players and even less have Blu-ray recorders. In conclusion, what counts is the content of the video, and less so the technical details of the equipment used to make it. Don't shoot the messenger.
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Dave Watterson
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Re: What is HD ?
Roy's right - content is king. But I'm still keen to at least try demystifying HD.
Roy mentions the term "3-chip"
- most of us know it means a camera with three separate imaging chips to record the red, green and blue aspects of an image - which results in a notably better picture than a single chip can achieve. But that has been around for decades. SD and HD cameras may both have three chips in them.
He also mentions "upscalers"
- these are essentially tiny computers which are fitted to a great many new television sets and video projectors as well as to some DVD players. They take a signal like our PAL standard 720 by 576 pixel image and turn it into a higher resolution like 1920 by 1080. They do this by interpolating (guessing) what should fit between the existing pixels. Imagine a picture of a sunset - the upscaler might figure out that a line between this light orange colour and the next slightly darker orange colour should be a colour somewhere between the two. It sounds Heath-Robinson* but actually works very well in most cases.
Of course it is an interim measure to "link up" standard definition and high definition. I think of it as like plumbing adapters to connect 15mm pipes to 22mm ones. If you have an upscaler in your DVD player and one in your projector it can be tricky to know which to use. Suck it and see, I suppose.
An upscaler is a great gadget to use until everything has gone HD. Unfortunately for our purpose here it helps blur the distinction between SD and HD.
Dave
* Sorry another bit of jargon. The term comes from William Heath Robinson an English cartoonist who often drew fanciful gadgets which seemed most unlikely to work in real life.
Roy mentions the term "3-chip"
- most of us know it means a camera with three separate imaging chips to record the red, green and blue aspects of an image - which results in a notably better picture than a single chip can achieve. But that has been around for decades. SD and HD cameras may both have three chips in them.
He also mentions "upscalers"
- these are essentially tiny computers which are fitted to a great many new television sets and video projectors as well as to some DVD players. They take a signal like our PAL standard 720 by 576 pixel image and turn it into a higher resolution like 1920 by 1080. They do this by interpolating (guessing) what should fit between the existing pixels. Imagine a picture of a sunset - the upscaler might figure out that a line between this light orange colour and the next slightly darker orange colour should be a colour somewhere between the two. It sounds Heath-Robinson* but actually works very well in most cases.
Of course it is an interim measure to "link up" standard definition and high definition. I think of it as like plumbing adapters to connect 15mm pipes to 22mm ones. If you have an upscaler in your DVD player and one in your projector it can be tricky to know which to use. Suck it and see, I suppose.
An upscaler is a great gadget to use until everything has gone HD. Unfortunately for our purpose here it helps blur the distinction between SD and HD.
Dave
* Sorry another bit of jargon. The term comes from William Heath Robinson an English cartoonist who often drew fanciful gadgets which seemed most unlikely to work in real life.
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billyfromConsett
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Re: What is HD ?
The form of HD which many of us have adopted is in the format of HDV.
HDV uses 1440 x 1080 pixels, but with oblong pixels, so they take up the room of square pixels that are 1920 x 1080. The screen ratio is naturally 16:9.
Because the files it uses are a form of mpeg2, you can get about 25ish minutes of footage onto a standard 4.5gb DVD, though it wouldn't play it directly, as it needs to read it more quickly than it can be read.
A Computer for the job - won't break the bank!
HDV is more easy on a computer than say the format of AVCHD (which uses the full 1920 x 1080) but an editing PC for HDV still needs a fast processor, at least a 2.5ghz twin core chip, and at least 2gb of ram. The hard disk needs to be able to read and write at over 35mb/sec - the speed a modern SATA drive will easily do.
HDV uses 1440 x 1080 pixels, but with oblong pixels, so they take up the room of square pixels that are 1920 x 1080. The screen ratio is naturally 16:9.
Because the files it uses are a form of mpeg2, you can get about 25ish minutes of footage onto a standard 4.5gb DVD, though it wouldn't play it directly, as it needs to read it more quickly than it can be read.
A Computer for the job - won't break the bank!
HDV is more easy on a computer than say the format of AVCHD (which uses the full 1920 x 1080) but an editing PC for HDV still needs a fast processor, at least a 2.5ghz twin core chip, and at least 2gb of ram. The hard disk needs to be able to read and write at over 35mb/sec - the speed a modern SATA drive will easily do.
Re: What is HD ?
Isnt it better to film in the same resolution as the resolution of a HD television ie 1920×1080 ie 1080p.
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billyfromConsett
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Re: What is HD ?
Not all hd tv's are that resolution are they?
Re: What is HD ?
Couple of thoughts. Strictly speaking PAL and NTSC refer to analog standard def systems. The only diffrence between N America and European HD is the frame rate, we in the USA are 30i or p you are 25. The advantage of the higher frame rate is that we don't get the flicker you can see on large light areas at 25 fps.
The obsession with 24p produces all the panning/movement problems we see with film and it still doesn't look like film. My view is that if you want it to look like film then shoot film!
As Michael Slowe has written elsewhere a well made SD DVD will look very good indeed if mastered from an HDV/HD master and played back to a high quality TV/Projector with a line doubler. Down resing from HDV certainly seems to deliver a high quality SD version.
I have made a number of short HD DVDs that play back on BluRay, they are encoded to AVCHD which is MPEG4H.264, not MPEG2 which is the regular DVD CoDec. As Billy says I can get about 25 minutes on a standard DVD.
ned c
The obsession with 24p produces all the panning/movement problems we see with film and it still doesn't look like film. My view is that if you want it to look like film then shoot film!
As Michael Slowe has written elsewhere a well made SD DVD will look very good indeed if mastered from an HDV/HD master and played back to a high quality TV/Projector with a line doubler. Down resing from HDV certainly seems to deliver a high quality SD version.
I have made a number of short HD DVDs that play back on BluRay, they are encoded to AVCHD which is MPEG4H.264, not MPEG2 which is the regular DVD CoDec. As Billy says I can get about 25 minutes on a standard DVD.
ned c
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Dave Watterson
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Re: What is HD ?
We are off again into complexities and sources of confusion.
Pixel Shape
Virtually all video pixels are oblong not square. That is why if you capture a 4:3 SD frame and put it into a graphics program you usually need to stretch it to 768x576 before it looks right. If you capture a 16:9 SD frame you have to stretch it to 1024 pixels wide. So that in itself is not a new idea.
It seems that HDV uses a slightly different size of oblong, but that it is working in much the same way as SD in the 16:9 aspect ratio. If you could hold a frame of HDV up to the light it would show slightly tall and thin people.
HDV
HDV is an entry-level format allowing a lower cost start in HD filming. It comes in two sizes: HDV 1080 and HDV 720.
Full HD uses 1920x1080 = 2,073,600 pixels making up a picture.
HDV 1080 uses 1440x1080 = 1,555,200 pixels making up a picture, 75% of full HD.
HDV 720 uses 1280x720 = 921,600 pixels making up a picture, 44% of full HD
SD’s 720x576 means 414,720 pixels make up a picture, 20% of full HD.
So either type of HDV is very much better quality than SD but not so good as full HD.
Compression
When Billy mentions MPEG2 we are off into another byway on the journey.
All consumer video is compressed to some degree in order that it can be processed, stored in cameras and other equipment and transmitted either over the air or on DVDs/Blu-Ray discs. One of the things that makes HDV practical for normal use is that the MPEG2 compression system is very good. It is used for DVDs and broadcast television.
There is a newer kid on the block: MPEG4, often referred to as H.264/MPEG-4 AVC. That compresses even better.
Television Sets
All sorts of sizes are being called “HD” …
A quick look at amazon.co.uk shows sizes of 1680x1050, 1440x900, 1280x1024, 1366x768. Many claim to be compatible with various other resolutions. Aaaargh!
AVCHD
This is a format developed for tapeless camcorders – those which record onto mini-dvds, hard drives or memory cards. It uses the newer, very efficient MPEG4 compression system. It does, however, require an editing computer between two and four times as powerful as one you would need for HDV. AVCHD camcorders are available for 720 and 1080 resolutions.
-Dave (whose brain is hurting)
Pixel Shape
Virtually all video pixels are oblong not square. That is why if you capture a 4:3 SD frame and put it into a graphics program you usually need to stretch it to 768x576 before it looks right. If you capture a 16:9 SD frame you have to stretch it to 1024 pixels wide. So that in itself is not a new idea.
It seems that HDV uses a slightly different size of oblong, but that it is working in much the same way as SD in the 16:9 aspect ratio. If you could hold a frame of HDV up to the light it would show slightly tall and thin people.
HDV
HDV is an entry-level format allowing a lower cost start in HD filming. It comes in two sizes: HDV 1080 and HDV 720.
Full HD uses 1920x1080 = 2,073,600 pixels making up a picture.
HDV 1080 uses 1440x1080 = 1,555,200 pixels making up a picture, 75% of full HD.
HDV 720 uses 1280x720 = 921,600 pixels making up a picture, 44% of full HD
SD’s 720x576 means 414,720 pixels make up a picture, 20% of full HD.
So either type of HDV is very much better quality than SD but not so good as full HD.
Compression
When Billy mentions MPEG2 we are off into another byway on the journey.
All consumer video is compressed to some degree in order that it can be processed, stored in cameras and other equipment and transmitted either over the air or on DVDs/Blu-Ray discs. One of the things that makes HDV practical for normal use is that the MPEG2 compression system is very good. It is used for DVDs and broadcast television.
There is a newer kid on the block: MPEG4, often referred to as H.264/MPEG-4 AVC. That compresses even better.
Television Sets
All sorts of sizes are being called “HD” …
A quick look at amazon.co.uk shows sizes of 1680x1050, 1440x900, 1280x1024, 1366x768. Many claim to be compatible with various other resolutions. Aaaargh!
AVCHD
This is a format developed for tapeless camcorders – those which record onto mini-dvds, hard drives or memory cards. It uses the newer, very efficient MPEG4 compression system. It does, however, require an editing computer between two and four times as powerful as one you would need for HDV. AVCHD camcorders are available for 720 and 1080 resolutions.
-Dave (whose brain is hurting)
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Roy
Re: What is HD ?
Well done Dave. your explanations are fairly clear and should suffice for those who wish to know, including me.
However can you explain this, which is a puzzle to me. I am using Premiere Pro 2 to edit HDV video. After editing a short few minutes test of HDV video, I found that I can export the timeline direct to a DVD using the Computer's burner. It does the job fairly quickly, It's not as good as using 6.5 timeline direct to a DVD recorder, but it works. All the settings on Pro 2 are set for HDV and yet it burns a DVD, and the DVD plays back on any playback unit. Am I right in assuming that the Pro2 programme automatically downsizes the timeline content to SD before burning the DVD. ROY
However can you explain this, which is a puzzle to me. I am using Premiere Pro 2 to edit HDV video. After editing a short few minutes test of HDV video, I found that I can export the timeline direct to a DVD using the Computer's burner. It does the job fairly quickly, It's not as good as using 6.5 timeline direct to a DVD recorder, but it works. All the settings on Pro 2 are set for HDV and yet it burns a DVD, and the DVD plays back on any playback unit. Am I right in assuming that the Pro2 programme automatically downsizes the timeline content to SD before burning the DVD. ROY
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Dave Watterson
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Re: What is HD ?
Sorry, Roy, you are going beyond my level of knowledge.
I think that if the DVD you output plays on any player then it must be SD ...
What happens if you export to a file? What is the resulting file - SD or HD?
Dave
P.S. I have just been reading Camcorder Buyer HD Ready magazine and though it is helpful, especially for those not prepared to spend over £1,000 on a camcorder, neither in reviews or its buyer's guide is it easy to discover what resolution each camcorder has! They seem to take the view that 1280x720 is enough to qualify for the HD label.
I think that if the DVD you output plays on any player then it must be SD ...
What happens if you export to a file? What is the resulting file - SD or HD?
Dave
P.S. I have just been reading Camcorder Buyer HD Ready magazine and though it is helpful, especially for those not prepared to spend over £1,000 on a camcorder, neither in reviews or its buyer's guide is it easy to discover what resolution each camcorder has! They seem to take the view that 1280x720 is enough to qualify for the HD label.
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Roy
Re: What is HD ?
Dave - If I export it to Movie. As far as I know its in HDV. And I am presuming that is what you would term a file, as it puts it on the hard drive as an Mpeg 2.
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tom hardwick
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Re: What is HD ?
[quote="Dave Watterson"]They seem to take the view that 1280x720 is enough to qualify for the HD label.[/quote]
And they're right to take that view Dave, as anything over and above 720 x 576 is classed as 'high definition' (or to be pedantic, 'higher definition'. And I feel we shouldn't be using the term 'full HD' when we talk about 1920 x 1080, as in no time this will be surpassed.
CDs were seen as high definition after vinyl and cassette tape, but then SACDs and DVDCDs came along. Paradoxically HDV camcorders don't record the audio as well as the DV camcorders before them and the world and his dog are happy listening to horribly compressed MP3 audio all day long.
tom.
And they're right to take that view Dave, as anything over and above 720 x 576 is classed as 'high definition' (or to be pedantic, 'higher definition'. And I feel we shouldn't be using the term 'full HD' when we talk about 1920 x 1080, as in no time this will be surpassed.
CDs were seen as high definition after vinyl and cassette tape, but then SACDs and DVDCDs came along. Paradoxically HDV camcorders don't record the audio as well as the DV camcorders before them and the world and his dog are happy listening to horribly compressed MP3 audio all day long.
tom.
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Dave Watterson
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Re: What is HD ?
Hi Tom,
I take your points ... but this thread started with the hope of explaining what the buzz-word of the moment, "HD", really means. I fear that it has become a marketing term which is very loose indeed.
Yes, anything labelled "HD" will be at least marginally better than the Standard Definition we know today. But I think a lot of people are going to be mightily pissed off when they find that their bargain "HD camcorder" or "HD tv" is actually much inferior to the ones I've been calling (for simplicity) "Full HD").
It will be a while before we all switch to Red camcorders and images 4,520 x 2540 pixels and more in size.
In the meantime any help you can give in cutting through the hype would be very welcome.
Dave
I take your points ... but this thread started with the hope of explaining what the buzz-word of the moment, "HD", really means. I fear that it has become a marketing term which is very loose indeed.
Yes, anything labelled "HD" will be at least marginally better than the Standard Definition we know today. But I think a lot of people are going to be mightily pissed off when they find that their bargain "HD camcorder" or "HD tv" is actually much inferior to the ones I've been calling (for simplicity) "Full HD").
It will be a while before we all switch to Red camcorders and images 4,520 x 2540 pixels and more in size.
In the meantime any help you can give in cutting through the hype would be very welcome.
Dave